1. Field of Invention
The present invention relates to a light emitting device. More particularly, the present invention relates to a light emitting diode structure.
2. Description of Related Art
A light-emitting diode has its characteristics of generating considerable brightness with low power. It can not only serve as a screen backlighting but also be used as the light-emitting element in a variety of lighting fixtures, such as light bulbs, lamps, tubes, plate lights, street lights and a variety of advertising signs and other kinds of lamps.
In order to save energy, manufacturers hope to make some powerful light-emitting diodes to produce greater brightness, such that the light-emitting diode structure has a constant innovative research and development, thereby changing the structure of light-emitting diodes to increase the light transmittance so as to enable the light emitting diode to be brighter.
A conventional light emitting diode structure contains an n-type conductive layer, a light emitting layer, and a p-type conductivity layer, and also includes different forms of current blocking layers, transparent conductive layers and electrodes according to different design purposes. FIG. 1 illustrates a top view of a conventional LED 50, and FIG. 2 illustrates a cross-sectional view of the conventional LED taken along A-A′ in FIG. 1. As illustrated in FIGS. 1 and 2, the conventional LED 50 has a transparent conductive layer 53, a p-electrode 55 and an n-electrode 56 on its upper surface. When the light emitted from the emitting multilayer structure 52 goes through an interface between the transparent conductive layer 53 and air, most of the light does not go out of the LED chip due to the total internal reflection. The light-emitting diode has a total reflection angle of about 24.5 degrees for an air interface. The total reflection at the interface between the transparent conductive layer and the air causes a lower light extraction rate, that is, only part of the light goes outside of the LED chip, but a large majority of the light is entrapped within the LED chip and finally converted into heat. Therefore, there is a need for manufacturers to innovate the light emitting diode structure so as to improve the light extraction.